Correction of color transparencies



Patented Se t. 23', 1930 ably of a single elementary color.

UNITED STATES PATENT OFFICE BOY J. POMEROY, OF LOS ANGELES, CALIFORNIA, ASSI ZGNOB OF ONE-ELLE TO PABA- JEOUNT FAMOUS LASKY CORPORATION, OF LOS ANGELES, CALIFORNIA, A CORPORA- TION OF NEW YORK (JORRIEG'JJIONv OF COLOR TRANSPARENCIEB Original application filed December 19, 1925, Serial No. 76,423. Divided and this application filed June 12,

1928. Serial No. 284,787. r

This invention has to do with photographic dye color transparencies, or, as they may be known, color dye-image photographic positives or negatives; such transparencies revealing their images in the depth of the colored dye pigment of which the images are composed. A transparency of this nature is nearly or quite uniformly transparent to light of its own color, but its transparency to light of the minus or complementary color varies with the density of the colored pigment of its dye-image.

This application is-adivision of my original patent entitled Methods of producing composite pictures, No. 1,673,019, date June 12, 1928. The subject matter claimed in the present application is particularly adapted to be practiced as an adjunct to the method of the saidoriginal patent, and is therefore herein particularly described in that connection, but without necessary limitation thereto. 1

A transparency of the nature referred to comprises a photographic color-dye image contained upon a transparent film, the dye used in preparing the image bein refer- It 's d e is perfectly pure and uniform in color, t e transparency will be perfectly and uniformly transparent to li ht of its own color. In practice, however, t e dye may contain impurities of various colors, and due to their presence a certain percenta e of light of the pure dye color is absorbe The-result is 'that the transparency image possesses a for instance, as a slight difierence in shade be- I a tween the transparency and the light which is used. Whatever the cause, it may become necessary in the practice of certain processes hereinafter described to correct or compensate this condition. And in doing this it may be required, as will appear later, that any such corrective measures do not substantially interfere with the value of the transparency the ima image to light'of another color, particularly 7 ing of my invention, but without intention of imposing a limitation thereupon, I shall describe my invention as utilized in connection with the method of producing composite pictures referred to above, and for this purpose I refer to the accompanying drawings, in which:

Figure 1 is a diagram representing a typical arrangement by which the method of makin composite pictures may be carried into e ect; and

Figure 2 is a diagram of the system of Figure 1 modified by the-present invention.

It willbe understood that the particular colors herein referred to are not a limitation upon the invention, and that'any colors may be used which have the samemutual relations to those herein selected for illustration. The method will be understood to be applicable to either positives or ne atives, the term positives and negatives being used throu hout in their'ordinary. photographic sense, t at is, a color-dye positive being an image in a single dye color of a scene as it actually appears, while a ne ative is the photographic reverse, eing the same color as before, but having t elights andshades reversed, as will be understood. The method of preparing such positives and negatives, althou known, will be hereinafter briefly in icated. Ishall first briefly describe the method of producing composite pictures as set out in my heretofore mentioned original application, and then show how the method of the present invention may be ap lied thereto. From this it will be apparent ow the present invention may be practiced in various other connections.

' In the method of producing composite pietures, a negative of the desired background or scene, if it be astill scene, is made upon a single plate, preferably of large'size, and in the ordinary manner. From this negative a positive of similar made but for the purpose of this positive I employ a bichromated gelatin so as to get what is known as a away from a warm water wash and thus produce the gelatin relief, as is well known.

Having obtained this'gelatin positive, it is v next dyed with a suitable dye, which for inwith which to illuminate the Y but pure 'ency is transparent an stance, may be of a blue color. Other colors may be used, blue being merely selected for the purpose of illustration. The positive as thus prepared has a tr arent' blueness over its whole surface, the fdepth of the blueness varying and by that variation showing the image of the background or scene that was origmally taken. To blue light, however, the transparency is almost uniformly transparent, as may be demonstrated by holding the transparency up to the light with a blue vfilter interposed, when the image substantiallg disappears. This test may not give perect results, however, for the reason that some white light may be able to pass through the blue filter, thus not producing pure blue light lue transparencyl. To light as so obtained the blue color m e deeper orheavier parts of the transparclear, and through these deeper blue parts substantially nothing lue light can pass; but through the lighter blue parts a proportionately larger amount of white light may pass, revealing in these parts a faint image when viewed closely. If, however, the transparent positive be held up to the light with a red (or substantially minus-blue) filter behind it, the transparent blue positive is transformed, in effect, into a black and white 'tive, appearing substantally as would a lack and white positive illummated withred light. This appearance red is due to the factfthat through the heavier blue arts only blue light can pass, and the ter passes substantially no such blue light at all, thus causing the heavier blue parts to appear dark; while in the lighter parts, the red light that passes through the filter can also ass at least partially through the blue positive behaves toward lightv of its complementary color exactly as does a black and white positive toiwhite li ht. And this.

fact is true not only of the co ors chosen for illustration, but of any pairof complementary colors. It is of course necessary that the colors. be substantially complementary, as light of acolor in between the two, as for initance ye ow, could partially pass through .cominglfrom the background;

.which corresponds to the ordinary motion picture camera lens, is focused upon the blue transparency and therefore also upon the image thrown by lens 10 upon it. Lens 14 is focused on the final negative 15 which, in this particular case, is illustrated as a motion picture film. The method is applicable to either motion or still photography, the process being described with motion pictures in mind because of its present great utility in that field Behind the subject 11 is a background 16, which is of a minus-blue color or in otherwords of a suitable red color. This background may also be illuminated by a light of the same color coming from a source such as is indicated at 17. I The function of the element 16 is-merely 'to illuminate the blue transparency with red lightso that the red background 16 maybe considered ply as a source .of uniformly distributed red light.

The subject 11 (usually in motion pictures tion) is illuminated. with blue light from a suitable source, as indicated at 18, the lights being so arranged that no red ht falls on the' subject and no blue light alls on the background.

Blue light from thesubject will pass through the blue transparency 12 substantially equally in all parts of that transparency,

- a subject includingthlngs or persons mmodue to its uniform transparency to blue over itswhole surface. ,Consequentlythe image of the subject that is finally thrown on the negative 15 by lens 14 is not interfered with by the varying blueness of the positive; and

that image in blue light finally thrown on negative 15 is, substantially, just the, same as if the-transparent positive 12 were not interposed at all. And the subject, of course, intercepts all red light from the background directly behind the subject. The result is thatfas to the subject, the final negative takes an image of thevsubject uninterfered with by the thin blue ye. It will thus be seen that the blue transparency or by the red light At t 'e'same time, the red light from the background illuminates all parts of the transparency 12- not occupied by the image of the subject; andthis illumination by red light I transforms that blue transparency, in effect, into a black-and white positive, as I have explained before. Consequently lens 13, takmgred light from the blue transparency,

ject. All this takes place simultaneously at a single exposure, so that final; negative 15 has cast upon it animage of the subject, in blue light, surrounded by an image of the background or scene in red light. The final negative thus receives the desired composite picture and upon development its shows that composite picture just as ifthe subject had been taken in the ordinary manner while actually in the depicted scene.

It may be, however, as has previously been stated, that the blue transparency is not perfectly transparent to blue light (shows a slight image when illuminated with blue light); and if this condition becomes sufficiently pronounced, the blue transparency may absorb enough blue light from the subject to cause an image of itself to be superimposed upon the image of the subject in the final negative. This condition may be remedied, according to the present invention,

in the following manner. A corrective transparent negative of the background scene of a selected color and tone preierably intermediate of the positive transparency color and the complementary colored light is made and registered with the transparency background positive, as at 19 in Fig. 2. In the present lllustrative. case, this corrective negative transparency may be of a color intermediate of red and blue-for instance, of a selected shade of yellow. Sucha yellow transparent negative may be made by a process similar to that by which the blue transparent positive is made, suitable dyes being used as is well understood in the art. This yellow-dye transparency negative, which is ordinarily made quite thin, has the property of absorbing a small proportion of the lue light,- but in the main is quite transparent to lue light. The transparency of the yellow transparency to red light is very hi h, little or no red light being absorbed.

he yellow dye trans arency negative 19, positioned in the optica s stem as indicated in Fig. 2, therefore, in eliect, adds a slight amount of opacity to the blue transparency as regards blue light; but since the yellow transparency is a negative, it adds a certain amount of opacity to the lighter blue parts while adding no appreciab e amount tothe heavier parts, as will be understood from a consideration of the inherent relation between the,

respective lights and shades of positives and negatives. he efiect as'regar s blue light is then that the lighter blue areas of thepositive become slightly more opaque with respect to the heavier blue areas, thus reducing the diii'e'rences between the-lights and shades and accordingly lessening the distinctness of the transparency image. With the proper choice of color and shade in the corrective transparency negative, the difierences between the lights .and shades of the transparency image need be reduced but slightly to do away entirel with any noticeable'image to blue light. 1 e yellow trans arency is suifi'ciently trans arent to blue ligiit that the transmission of b lue light from the subject to the final negative is not materially interfered with; and as the yellow transparency may be perfectly trans arentto red light for is not affected. Briefly summing up, the fact that the yellow transparency is a negative causes it to add opacity to the thinner parts of the blue positive without adding any substantial amount of opacity to the heavier parts of the blue positive. Being of a yellow color, and thus being capable ofpartially passing blue light and of nearly perfectly passing red light, it will be seen that it will add to the more transparent blue portions just the slight additional opacity to blue that is desired; and at the same time it will not noticeably change the transparency to red light.

It will be seen that the essence of the inall practical purposes, t e passage of red light vention lies in the use of a corrective transparency negative of a selected color and shade quite transparent to either red or blue light, but which has the power to absorb enough of blue light that any transparency image to blue lig t is precluded.

Stated broadly, the requirements are that the transparency negative must be of a color and shade to have a relatively high and uniform transparency to light both of the transparency color and its complementary at which has enough absorption to 'ght of the trans arency color to preclude the formation 0 an image to light of that color. It will be apparent, upon consideration of the fundamentals involved, that other colors aside from yellow meet the requirements for the corrective transparency. For instance, a light pink or even a neutral gray may be utilized. The use of a gray, or\ of other colors which. will absorb some of. the red light, while entirely operative, is not to be color,

llt

preferred as the contrasts between the lights and shades of the transparency image to red light are somewhat reduced in this case. In fact, theoretically the corrective transparency negative may be of any color, exclusive of the color of the transparency positive, or-

may beef 9, neutral gray, it being merely required that the corrective transparency absorb some light of the transparency positive .color, and transmit a large amount of both the transparency positive color and its complementary color. It is always possible and preferable, however, to select a color for the negative which has the above required pro erties, and which in addition is ractic y perfectly transparent to light '0 the color 4 r 1,77e,eee

complementary to that of thepositive trans parency, as is the yellow transparency to red light in the above illustrative case.

It will be understood that the invention 5 is not limited to the specific colors set out above, as it is entirely practicable to reverse the relation of the two colors, making the transparency red and the background light blue; and. furthergthe method is applicable not only to red and blue, but to any air of complementary colors, it being mere y nec-" essary in any case to select a transparency negative color having properties relative to the color of the transparency positive as hereinbefore set out. The invention is further not to be limited to the specific adaptation to the method of producing composite pictures, but only as defined in the following claims. vI claim: I J

1. The method of correcting the transparency of a colored transparent dye image to light of its own color that includes, placing in registration with the image a corresponding relatively negative image in transparent dye of a color intermediate the first mentioned color and its'complement.

2. The method ofcorrecting the transparency of a colored trans arent dye image to light of its own color that includes placing in registration with the image a corresponding' relatively negative image, the negative image being of a color other than that of the color of the transparency.

In witness that I claim the foregoing I have hereunto subscribed my name this 8th day of June, 1928;

- ,ROY J. POMEROY. n 

